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A series of monoiodoborane adducts LBH 2 I (L = N(CH 3 ) 3 pyridine, 3-methylpyridine, 4-methylpyridine or (C 6 H 5 ) 3 P) has been prepared. Ideally, the addition of suitable amines, phosphines or trimethylarsine to a benzene solution of these adducts would be expected to yield boronium salts containing two different donors coordinated to a central boron atom. These salts, of the general formula LL′BH 2 I, were formed in several instances (L′ = (CH 3 ) 3 P, (C 6 H 5 ) 3 P, (CH 3 ) 3 N). Six previously unreported boronium cations have been characterized. The iodide salts of these boronium cations may be easily converted to their hexafluorophosphate analogs except for the large ligands such as (C 6 H 5 ) 3 P or 3-methylpyridine. In contrast, trimethylarsine reacted with 4-MepyBH 2 I in benzene to give 4-MepyH + I − and [(CH 3 ) 3 AsI] + I − . The proton and boron NMR spectra of all species were investigated when experimentally feasible.

The addition of an equivalent of Cl 2 , Br 2 or I 2 to a solution of Na[H 3 BCN] in glyme (1,2-dimethoxyethane) yields the cyanoborane cyclic oiligomers previously reported. The addition of an excess of a Lewis base (e.g. a pyridine, a tertiary amine or a tertiary phosphine) to the cyanoborane yields a cyanoborane adduct, LBH 2 CN. The addition of an excess of chlorine yields a solution believed to contain [glyme]-BH 2 CN. This solution reacts slowly with Lewis bases (L) to yield LBH 2 CN, and small amounts of chlorinated cyanoborane adducts. The proportion of chlorinated products relative to LBH 2 CN increases as the amount of moisture in the reaction mixture increases and as the base strength of L is reduced. The chlorination of LBH 2 CN in moist benzene yields LBCl 2 CN as the principal product when L is pyridine, while a complex misture is obtained when L = (C 2 H 5 ) 3 N.